The section you are talking about is witnessing of the parents consent form.
Each parent must have their signature witnessed to ensure that no parent gets a passport for a child behind the back of the other parent.
The form makes clear who can act as a witness. I think it is a lawyer, member of the clergy, school principal, garda, Doctor, accountant, Peace commisioner.
Read the section at the top of that page carefully and it should be clear.
Thanks seen it and a Garda can sign both